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Implications of the spatial variability of infiltration-water chemistry for the investigation of a karst aquifer: a field study at Milandre test site, Swiss Jura

Perrin, J. ; Jeannin, P.-Y ; Zwahlen, F.

In: Hydrogeology Journal, 2003, vol. 11, no. 6, p. 673-686

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    Title
    • Implications of the spatial variability of infiltration-water chemistry for the investigation of a karst aquifer: a field study at Milandre test site, Swiss Jura
    Author
    • Perrin, J.. Centre of Hydrogeology, Neuchâtel University, 11 rue Emile Argand, 2007, Neuchâtel, Switzerland
    • Jeannin, P.-Y. Centre of Hydrogeology, Neuchâtel University, 11 rue Emile Argand, 2007, Neuchâtel, Switzerland
    • Zwahlen, F.. Centre of Hydrogeology, Neuchâtel University, 11 rue Emile Argand, 2007, Neuchâtel, Switzerland
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:317818
    Summary
    The Milandre test site is an ideal karstic aquifer for studying the spatial heterogeneity of groundwater chemistry. Numerous observation points can be sampled: the spring, the underground river and its tributaries, and boreholes at different depths. The main causes of the spatial variability of the chemical parameters are: nature and localisation of the input, the structure of the infiltration zone, chemical reactions (transit time vs. reaction kinetics) and mixing of different waters. Physico-chemical data on springs discharging from the karstic system represent the sum of this spatial heterogeneity. Therefore, it is difficult to interpret the global-chemical response with a simple mixing model of the aquifer subsystems (runoff, matrix reservoir, epikarst). Chemical constituents related to agricultural inputs show important seasonal variations (coefficient of variation approximately 15%) and parameters linked to rainfall (δ18O) and to the aquifer (Ca2+, HCO3 −) present variations of less than 5%. This result indicates the importance of water storage in the epikarstic aquifer for periods of a few months